Metal-catalyzed olefin metathesis reactions serve as a springboard for the development of a range of regioselective and stereoselective processes. These processes are important steps in the chemical synthesis of complex organic compounds and polymers. In particular, these reactions often are crucial steps in medicinal chemistry for small molecule synthesis. Organo-metallic catalysts, particularly transition metal complexes based on osmium, ruthenium or tungsten, are used in many such organic transformation reactions.
The synthesis and catalytic activity of ruthenium-based complexes which can efficiently catalyze ring-opening metathesis (ROM) and ring-closing metathesis (RCM) of dienes that contain terminal olefins has been reported for example, by Kingsbury, J. S.; Harrity, J. P. A.; Bonitatebus, P. J.; Hoveyda, A. H. J. Am. Chem. Soc. 1999, 121, 791-799; Harrity, J. P. A.; Visser, M. S.; Gleason, J. D.; Hoveyda, A. H. J. Am. Chem. Soc. 1997,119, 1488-1489; and Harrity, J. P. A.; La, D. S.; Cefalo, D. R.; Visser, M. S.; Hoveyda, A. H. J. Am. Chem. Soc. 1998, 120, 2343-2351. Because of the risk of metal contamination of the resulting product, and due to the cost of organometallic catalysts, recovery and reuse of such catalysts is important. Kingsbury, et al. showed that an organometallic rutheniun-based catalyst could be recovered from the reaction mixture by silica gel chromatography in high yield and reused in subsequent C—C bond forming reactions. Kingsbury et al., supra. However, there are several shortcomings in the prior ant recyclable metathesis catalyst, including that it is useful mostly for substrates that contain terminal alkenes. In certain cases, due to co-elution, isolation of the catalyst from the substrate is problematic.